Optimum metallic-bond scheme: Theoretical study of geometric structures for ground-state sodium clusters

We present an optimum metallic-bond scheme to study the geometric structures of sodium clusters Na_n(n⩽15) systematically by combining the characteristics of metallic bonds and the first principle molecular dynamics simulation. The scheme provides an optimum way to examine almost all stable structures of sodium clusters and to determine their ground state structures. It is interesting to note that for the larger sodium clusters (13⩽n⩽15), there are some plane-like substructures on their surfaces, which resemble the fragments of the (110) plane with the highest atomic area density in the bulk bcc sodium crystal. We also propose a possible way to understand the formation of large icosahedral sodium clusters (1500<n<22000).